Question: Consider the function, f, of two variables defined by f(x,y) = (x^2 - 9)*sin(y). Find all the stationary points of f and classify each of them as either a local maximum, local minimum or a saddle point.

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- Jan 4th 2013, 05:14 AMDiamondVH123Differentiate two variables and find stationary point
Question: Consider the function, f, of two variables defined by f(x,y) = (x^2 - 9)*sin(y). Find all the stationary points of f and classify each of them as either a local maximum, local minimum or a saddle point.

How would I answer this question? - Jan 4th 2013, 05:30 AMa tutorRe: Differentiate two variables and find stationary point
At the stationary points $\displaystyle f_x=f_y=0$.

To classify them you need to consider $\displaystyle f_{xx}, f_{xy} \text{ and } f_{yy}$.

This is all in your notes presumably and it's quite routine.

There are some good videos out there and of course there's Wikipedia.